It's always nice when a role player gives you an unexpected contribution in a big game.

Mario Chalmers put a smile on Erik Spoelstra's face in Game 4 of the NBA Finals by scoring 25 points, including 12 in the fourth quarter.

It's unlikely Chalmers will put together another effort like that as Miami attempts to secure the NBA championship in Game 5 on Thursday in South Florida. And Spoelstra won't be expecting it.

After all, prior to that breakout effort in Game 4, the Heat's point guard had amassed a total of 17 points in the first three games of the series combined.

Inconsistency is the hallmark of any role player and you take what you can get on any given night.

To win an NBA championship, however, your stars must deliver and for the most part they have on both teams during the 2012 Finals. LeBron James has been spectacular for the Heat while Dwyane Wade and Chris Bosh have done more than enough for Spoelstra.

On the other side Kevin Durant, despite foul trouble in a few games, and Russell Westbrook, albeit with his normal mental miscues, have brought it for Scott Brooks. The third part of Oklahoma City's equation, however, has been a no-show.

You can cite several factors as to why the Thunder are on the brink of elimination but James Harden's incomprehensible slump has to be at the top of any list.

Harden, the NBA's reigning Sixth Man of the Year, has scored just nine and eights points, respectively, in Games 3 and 4 at American Airlines Arena, shooting a miserable 2-for-10 in each contest.

Harden also scored just five in Game 1 and is averaging 10.8 ppg overall in the series, six below his regular season average. His three single-digit scoring games in The Finals equal the number he had in the entire regular season.

"My mechanics and everything looks good, feels good," Harden said on Wednesday. "Even when I shot the ball (Tuesday) night, a couple threes and it rattled in and out, I think one hit the back rim, they felt good, they just didn't go in."

Too often Brooks has had Harden on the floor without Durant or Westbrook, making him OKC's top offensive option. Spoelstra has scouted the Arizona State product well and understands he loves to split a double team with a long dribble. The Heat have been extremely aggressive in taking that away and Harden has not adjusted.

His poor play is starting to wear on his psyche. Harden failed on a fast break in the fourth quarter of Game 4 when getting caught between a lay-up and dunk with Wade chasing him. He also uncharacteristically came up empty on some rather easy open looks.

"I have a lot of confidence in my shot," Harden said. "Just by talking and putting the work in every single day. It's definitely frustrating when those shots get open and don't go in, but you've got to continue to play."

In Harden's case that was made tougher when he bruised his left hand in Game 4. The embattled star had the hand wrapped up prior to practice on the off day and was seen icing it but he will give it a go as OKC tries to extend things and send the series back to the Sooner State.

Something they can only accomplish if Harden stops playing like a member of the supporting cast and starts playing like James Harden.